NF-Y-type transcription factors play an important role in regulating plant growth and development and mediating plant resistance to abiotic stress. This study investigated the molecular characteristics, expression pattern in response to drought stress, and biological function in mediating plant drought tolerance of a transcription factor gene TaNF-YA1 belonging to the wheat NF-YA family. TaNF-YA1sequence was highly similar to TmNF-YA9 of Triticum monococcumin. Under drought treatment, the expression of TaNF-YA1 in roots and leaves increased continuously and peaked at 24 h after treatment, which remained stable until 48 h after treatment. In addition, the gene transcripts in roots and leaves decreased gradually when plants were recovered to normal condition after 48 h of drought treatment.Compared with the wild-type(WT) control, the growth vigor of the tobacco lines overexpressing sense TaNFYA1(Sen 1 and Sen 2) was enhanced under drought treatment, showing increasedplant size, fresh and dry weight of root. Moreover, these transgenic lines displayed enhancedability of photosynthetic carbon assimilationactivity of cellular antioxidant enzymes, and increased stomatal closure rate andwater holding capacity in the isolated leaves after drought stress. The expression levels of the antioxidant enzyme genes(NtSOD1.1, NtCAT2.2 and NtPOD4.1)and root development-associated genes(NtPIN1 and NtPIN4) were significantly increased in Sen 1 under drought treatment in comparison with the WT plants. Consistently, the tobacco lines expressing antisense TaNF-YA1(Anti 1 and Anti 2) showed decrease in plant growth, dry matter accumulation, physiological parameters(photosynthetic physiological parameters, cell protective enzyme activity, stomatal closure rate, water holding capacity of leaf) and drought related gene expressions. This study suggested that TaNF-YA1 promotes root development, photosynthetic assimilate production and homeostasis of cellular reactive oxygen species(ROS), and responds to drought stress to regulate the physiological and biochemical processes related to plant drought resistance, contributing to enhancement of the plant drought resistance.

In order to solve the problems of rational nitrogen (N) distribution in Heilonggang area in Hebei Province to increase yield,quality and N use efficiency of wheat,we analyzed the effects of different N base topdressing ratios on photosynthetic characteristics,grain yield and protein content of strong gluten wheat Gaoyou 2018 in the field of the light loamy soil in the field.There were five treatments including the control without N fertilizer (N0) and four treatments with base topdressing ratio of N fertilizer 3:7 (N1),4:6 (N2),5:5 (N3) and 6:4 (N4).The results showed that there was an increase followed by a decrease of the net photosynthetic rate,transpiration rate,stomatal conductance,SPAD value,plant dry matter and N accumulation,N efficiency,grain yield and protein content with the increase of base topdressing ratio of N fertilizer.While the intercellular CO₂ concentration of flag leaves decreased first and then increased.The net photosynthetic rate,transpiration rate,stomatal conductance and SPAD value of flag leaf were the highest under treatment N2 and showed increases by 1.70%-10.58%,1.40%-9.49%,0.81%-12.36%,0.29%-5.33%of that of the other N treatments,respectively.The intercellular CO₂ concentration was the lowest under treatment N2.The dry matter and N accumulation at grain maturation stages under N2 treatment were significantly higher than that in other N treatments by 11.77%-29.58%.Grain yield under N2 treatment was 1.05-1.08 times higher than the other N treatments.Under treatment N2,N partial productivity,apparent recovery and agronomic efficiency were significantly higher than those in the other treatments by 5.50%-8.10%,16.15%-21.23%and 19.43%-30.54%.The contents of albumin,glutenin and total protein in grain also increased by 7.86%-11.76%,3.06%-8.78%and 4.73%-7.22%,respectively,under N2 treatment.Therefore,the base topdressing of N fertilizer at the ratio of 4:6 can improve the photosynthetic characteristics of flag leaves,delay leaf senescence,promote the dry matter and N accumulation of plant,increase grain protein formation and improve N efficiency of strong gluten wheat on light loamy soil.It is a recommended method for rational application of N fertilizer.